Bone defects may be caused by a number of different factors, including but not limited to trauma, pathological disease or surgical intervention. Because bone provides both stability and protection to an organism, these defects can be problematic. In order to address these defects, compositions that contain both natural and synthetic materials have been developed. These compositions may, depending upon the materials contained within them, be used to repair tissues and to impart desirable biological and/or mechanical properties.
Among the known bone repair materials and bone void fillers is autologous cancellous bone. This type of bone has the advantage of being both osteoinductive and non-immunogenic. Unfortunately, this type of bone is not available under all circumstances. Moreover, donor site morbidity and trauma add to the limitations of autologous cancellous bone. One alternative to autologous bone is allograft bone. Unfortunately, allograft bone has a lower osteogenic capacity than autograft bone, has a high resorption rate, creates less revascularization at the bone defect site, typically induces a greater immunogenic response and may result in the transfer of certain diseases.
In order to avoid the issues that attach to the use of autologous and allograft bone, one may use synthetic materials. However, known synthetic materials suffer from one or more of the following drawbacks, including unacceptable workability, handling and setting parameters; insufficient density; undesirable absorption rates; and an inability to impart adequate stability.
Another issue arises when therapeutic agents are added to the bone repair materials and bone void fillers. Currently, ceramic settable cements exist that trap therapeutics agents within them and then the therapeutic agents are released as the ceramic resorbs. These settable cements do not make good bone grafting materials due to their lack of porosity.
Accordingly, there is a need for new defect fillers that have a therapeutic agent, such as an antibiotic, released from highly porous bone void fillers as the new bone grows within the bone void filler matrix.